From normal mode coupling to lasing in a III-V semiconductor microcavity

Summary form only given. Semiconductor microcavities will be described which exhibit record vacuum Rabi splitting-to-linewidth ratios because of the narrow linewidth of the InGaAs/GaAs quantum wells grown inside the high-finesse GaAs/AlAs cavity. When one of these microcavities with the exciton peak and cavity mode in resonance is excited resonantly or nonresonantly with cw or 100-fs-pulsed light, the two transmission peaks go down with negligible change in the splitting. At sufficiently high density the exciton-cavity coupling becomes too weak, and the system returns to the perturbative regime of irreversible emission yielding a single Fabry-Perot peak which results in the usual vertical-cavity lasing above threshold. Transfer matrix calculations of the microcavity transmission using measurements of the nonlinear absorption of the exciton resonance show that this unusual nonlinear behavior results from the fact that the exciton line broadens with little reduction in oscillator strength. The broadening increases the absorption at the normal-mode-coupling peaks thus reducing their transmission, and the splitting changes very little because the oscillator strength is nearly constant. The data are also in agreement with a microscopic theory for excitonic nonlinearities and light propagation in semiconductor microcavities for varying electron-hole densities. The nonlinear susceptibility of quantum confined excitons is determined from quantum kinetic equations including dephasing due to carrier-carrier and polarization scattering. The luminescence and transmission have also been studied as a function of cw and 100-fs excitation intensity and as a function of exciton-cavity detuning